This invention relates to a vehicle suspension device and more particularly to such a device of the type which includes a hydraulic shock absorber and a spring unit communicating with the interior of the shock absorber and having a pneumatic spring chamber defined by an elastomeric diaphragm on one side thereof, the spring chamber being filled with compressed air or gas so as to bear a compressive load imposed upon the shock absorber.
The conventional vehicle suspension devices of the type described have the advantage that under high load conditions, the spring rate of the pneumatic spring chamber is increased in proportion to the load increase so that the shock absorber can act to effectively bear the increased load without affecting the comfort in riding of the vehicle, to which the devices are fitted, but have the disadvantage that under low load conditions, the spring rate is greatly reduced to enlarge the amounts of extension and contraction of the shock absorber. In other words, the shock absorber has a tendency to overrespond to load variations to amplify pitching, rolling and/or vibratory motions of the vehicle, thereby reducing the maneuverability thereof to a substantial extent.
Therefore, this invention is intended to provide a vehicle suspension device of the type described which is capable of eliminating the abovementioned deficiency inherent to the conventional devices so as to support the body of a vehicle in its most stable attitude irrespective of the load condition without any appreciable loss of comfort in riding.
The above and other objects, features and advantages of the invention will more fully understood from the following description when taken in conjunction with the accompanying drawings, which illustrate one preferred embodiment of the invention.